
Differential Equations Ordinary and Partial Differential Equations Math Forum 
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December 7th, 2016, 10:30 AM  #1 
Newbie Joined: Nov 2016 From: Greece Posts: 13 Thanks: 0  pde
I need a hint for this exercise!partial de.jpg 
December 7th, 2016, 10:44 AM  #2 
Senior Member Joined: Sep 2015 From: CA Posts: 765 Thanks: 401 
I'd assume spherical symmetry and that the neutron density depends only upon $r$ and $t$. You'll have to take the Laplacian in spherical coordinates. See if that gets you anywhere. 